Internal combustion engines typically use water based coolant systems for thermal management. A typical engine cooling system includes an engine driven pump for circulating coolant through the engine. The coolant is circulated through various engine components, for example, an engine crankcase, a cylinder head, one or more exhaust gas recirculation (EGR) coolers, turbocharger inter-stage coolers, and so forth. Coolant from the pump is usually cool, while coolant returning from the engine is usually hot. Heat generated by engine components, for example, combustion cylinders included in an engine crankcase, is transferred typically through conduction and/or convection to the circulating coolant.
Heat is removed from the coolant in a radiator. Before entering the radiator, the coolant passes through a thermostat which may bypass the coolant around the radiator to the pump inlet to maintain the coolant entering the engine at an elevated operating temperature by not cooling the coolant if the coolant temperature is below a predetermined value. However, since the coolant progressively accumulates heat as it passes through or over a series of engine components, sometimes circulating coolant may be at too high a temperature locally when it reaches a specific engine component, such as an EGR cooler, and may cause less than optimal performance of that component under certain operating conditions.
Accordingly, there is a need for management of coolant circuits in internal combustion engines that allows for optimal operation of various components of the engine.